AusBonsai

Fire burn and cauldron bubble .
I have a lot of old potting mix and for me this stuff is not cheap , diatomite , pumice , zeolite and such . I've been reusing it because I'm a cheap skate . I've basically been soaking it in water for a month to kill off any weed seed and then flushing it over an old fly screen with a hose to remove any fines . I am now taking it the next step and sterilising it with heat to make sure there are no nasty bugs . So each night I've been filling a pot ad bringing it to the boil for ten minutes or so . Cheers Sno

how's it smell?

Frogs and snails and puppy dog tails .

Frogs and snails and puppy dog tails .

Good job Sno. This is far better than just reusing it. Reuse without dealing with possible problems can only lead to problems.
Another grower I know uses an old electric frypan to sterilise (sorry, we can't actually sterilize without an autoclave so the correct term should be: sanitize). I put cutting mix and occasional potting mix through the microwave before reuse.

I bought a big old pressure cooker second hand and "autoclave" my used mix in that (after floating off the organic stuff). 12 mins at over 100 degrees is as close to sterilising as you can get without a proper machine. I have noticed that the slow release fertiliser balls come out intact but are very easily squashed so, as Shibui has suggested before, it may be worth bearing in mind that the progressive release of fertiliser will be disrupted/ accelerated.

I do re-use some of my mixes and all I have ever done was sieve it and then put it in sealed plastic bags and then put the bags in the sun for a week or so.
But this witches brew method takes it to a new level!